A lot of animals can only survive under very
specific conditions. If you mess with their habitat, they start
to die out. Others are a lot more versatile, and can adapt
when their environment changes. But a few animals are really, really good
at dealing with extremes -- like, way better than we humans are. We’re talking extreme heat and very little
water. Lack of food. No sunlight. Nuclear disaster. All of those scenarios might mean the end
of the world for humans, and some of them could probably wreck the planet enough to
wipe out all life, eventually. But these 9 animals do have a decent chance
of survival. Say there’s a Mad Max-style apocalypse,
and we end up with a desert planet that’s hot and almost completely dry. Anything that survived would need to be able
to withstand high temperatures and live on very little water. The dromedary camel fits that bill, and its
secret is in the hump on its back. This hump isn’t full of water, though. It’s actually fat. And there are a few reasons why a big ol’
lump of fat is helpful in the desert. Most mammals have fat distributed around their
bodies, but camels keep it all up on their backs. Fat is insulating.This is why seals and whales
have big coats of blubber: It keeps them warm. But obviously camels don’t need to keep
warm when it’s already blazing hot out, so they pile it all in one place. Also, fat is a nice energy reserve when you’re
traveling across the desert with little food. Then there’s the fact that breaking down
fat into energy has a helpful byproduct: Water. The thing is, to take in enough oxygen to
break down all that fat, the camel has to breathe a lot. But when you breathe you exhale water vapor,
so it should actually be a net loss of water for the camel. The camel gets around this problem by re-absorbing
water from the air as it breathes out. A camel’s nasal cavity has a ton of surface
area, all covered with tissue that water can stick to. As air passes by, the water gets drawn out
and stays inside the camel. Camels can go for weeks or even months without
a drink of water this way. There’s another mammal that might not need
to drink water.../ever/. Merriam’s kangaroo rat is a North American
rat. It isn’t actually related to kangaroos -- it’s
just named that way because it gets around by hopping. Its body also happens to be incredibly good
at retaining water -- Merriam’s kangaroo rats seem to get all the hydration they need
from the seeds they eat. It’s enough water for them because they
use it incredibly efficiently. They don’t sweat or pant to cool off, and
even their waste has almost no water in it. Once water’s in their body or generated
by their metabolism, they hang on to it. If you offered a Merriam’s kangaroo rat
a glass of water, it’d probably be like, no thanks, I just had seeds this morning. Merriam’s kangaroo rats are currently threatened
in some places because of humans taking over their habitat, but if water suddenly becomes
harder to find, we’ll be the ones in trouble. Then there’s the Sahara desert scavenger
ant. An insect so hardcore that when the temperature
gets too hot for other insects to handle, it feasts on their corpses. These guys would be the ultimate winners on
an overheated planet. There are several heat-tolerant species of
desert ants, but the Sahara one is the all-time champion. It actively goes out and looks for food at
temperatures higher than fifty degrees Celsius. In those conditions the surface of the sand
itself is closer to seventy -- the temperature of an oven on the lowest setting. And -- I really can’t let this go--their
food source is other insects who died because it was just too hot. They raid the bodies of their fallen comrades. How very incredibly post-apocalyptic of them. They outlast other insects in three ways. First, they’re super speedy, so they can
zip across burning sands. They also have long legs that lift them high
above the surface--proportionally long for an ant, that is--since the further you get
from the sand, the cooler the air. And for the same reason, they’ll often climb
plant stalks to get as far from the sand as possible and cool off. Now let’s talk about the opposite extreme. What if the sun totally disappeared, in some
comic book villain’s plot to destroy all life on Earth? Well, the plan wouldn’t work, because not
all life on Earth gets its energy from the sun. Giant tube worms live at the bottom of the
ocean where light can’t reach, around ocean vents that spew boiling water and chemicals
that, to us, would be deadly. Their secret to success is their symbiotic
relationship with some very strange bacteria. The hydrogen sulfide that comes out of deep
sea vents is toxic to most forms of life, but the bacteria use it to get energy. These bacteria also produce organic molecules
that the tube worms need to live. In return, the bacteria get to live inside
the tube worm’s body cavity, which is relatively safe and sheltered. So, if the sun were to vanish, as long as
the deep sea vents still functioned, these worms would be just fine. Until the oceans froze, that is. Speaking of freezing: What if the planet got very cold? Well, I’m happy to report the Antarctic
toothfish would probably be just fine. This fish lives in waters so cold, its tissues
should freeze solid. But they don’t, because it has a gene for
antifreeze. It’s not like the antifreeze that you put
in your car. It’s a glycoprotein [GLY-coh-protein], a
molecule made of both amino acids and sugars. This glycoprotein circulates in the blood,
binding to any ice crystals floating around in the bloodstream and stopping them from
getting bigger. Then, the fish can eliminate both the protein
and ice from its body. This biological antifreeze has actually evolved
more than once, in both Arctic and Antarctic fish. Which makes total sense, considering how cold
it gets in both of those places. So these fish species would be able to go
on feeding and swimming happily in frigid oceans where most animals would die. Survival isn’t all about temperature . Sometimes
there’s just very little food available. And in that case, some animals can afford
to wait until things get better. Take the ocean quahog [KOH-hog], a bivalve
mollusc that doesn’t seem to age. One specimen was confirmed to be 507 years
old when it was discovered. It was nicknamed Ming, after the Chinese dynasty
in power when it was born. How is it possible for an animal to live so
long? Scientists think the ocean quahog has two
main adaptations: First, it has a very slow metabolism, using
only a tiny bit of oxygen at a time. And oxygen use might have a lot to do with
aging, since the byproducts of oxygen metabolism, called free radicals, are damaging to cells. So the ocean quahog is very, very good at
limiting free radical damage to its cells. But some biologists don’t subscribe to this
free-radical idea, and there may also be some genetic secret to the quahog’s longevity
that we haven’t discovered yet. Either way, if food is scarce, the quahog
doesn’t care much -- it’ll just slow down its growth for a while, biding its time. Even with very few resources and just a trickle
of oxygen, these things can go on for hundreds of years. But there’s another animal that has an even
weirder trick. The immortal jellyfish -- which we’ve talked
about before -- can literally age backwards. Normally, jellyfish reproduce by developing
from a tiny larva into a polyp. Then, the polyp settles down on the ocean
floor and buds to give off medusae [meh-DOOS-aye], the familiar bell-shaped creatures we think
of as jellyfish. And if an immortal jellyfish medusa is injured
or faced with starvation, it can turn itself back into a polyp. During this process, called reverse development,
the jellyfish’s cells revert to a sort of blob that doesn’t do much. And while that blob is developing into a polyp,
it doesn’t need a lot of food. The polyp then turns into medusae genetically
identical to the original -- meaning that if the oceans don’t have much food, the
immortal jellyfish can just start over and try again until things look better. Another way the world might end? Nuclear catastrophe. The radiation that comes from nuclear blasts
shreds DNA like paper, so most forms of life have a rough time dealing with it. But people often talk about cockroaches sticking
around even if we humans wipe ourselves out with nuclear weapons. And there’s some truth to that. Cockroaches can withstand radiation doses
that would kill a human. They’ve been spotted alive and well in the
wake of nuclear explosions, and they seem to be able to handle at least ten times more
radiation than humans can. That said, it’s not just cockroaches. /All/ insects are more resistant to radiation
than humans. We’re not exactly sure why this is, but
there are a couple of running theories out there. For one thing, just like the ocean quahogs,
insect cells seem to be very good at resisting damage by free radicals. They’re also better at repairing their DNA
on ce it’s damaged -- even in cases where human cells would die, insect cells just fix
themselves and keep going. So insects in general are probably better
prepared to cope with a nuclear disaster than humans are. Cockroaches included. But there are tiny freshwater invertebrates
that even put roaches to shame in the radiation resistance game. They’re called bdelloid rotifers [DELL-oid
ROE-tih-fers], and their lives are just incredibly weird. See, unlike most animal species, bdelloids
reproduce asexually. Most animals use sexual reproduction as a
way to introduce variety in their gene pools, which makes it harder for threats to wipe
out the whole population. But the bdelloids have been going strong without
sex for 80 million years. Instead, they change up their gene pool by
stealing DNA from other species. Scientists haven’t quite figured out how
rotifers come by DNA from other species, but we do know that they’ve pilfered genes from
plants, bacteria, and fungi. This gives the rotifers a varied gene pool
even without sexual reproduction, but also makes them resistant to radiation. To steal DNA, they have to be pretty good
at joining together separate pieces of DNA. Which means if radiation messes with their
DNA, they’re really good at fixing it. So there are plenty of animals with survival
skills that might make us humans seem relatively fragile. And no matter what kind of planet we leave
behind, odds are that some animals will last longer than we will. Thanks for watching this episode of SciShow,
which was brought to you by our patrons on Patreon. If you want to help support this show, just
go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow
and subscribe!
Not even a mention of tardigrades!
Also, that dude needs to rethink his facial hair/regular hair choices.